How can i make something Invisible if the Light is on?
First click the camera icon in the outliner to be active or inactive then you insert a keyframe .You insert a keyframe by pressing the letter I while the mouse is over the camera icon.  Or context click to see the menu appear with a choice insert keyframe.

I suggest inserting at least 3 keyframes and traveling through the frames to see how the setting is maintained until the next keyframe.  Look at the camera icon and see if it become bright and then less bright or muted while moving the frame position.



The render visibility camera icon and the 3D View visibility eye icon near the arrow. Yellow indicates a keyframe. Image above.

Please know that for options and convenience the camera render icon does [not] affect the 3D View.  You must press render to see the difference.  You can animate 3D View visibility of the [Person] with the 3D View eye icon in the outliner near the camera icon... and that is your choice. It may be useful to know where the [Person] is, even if [ Person] is not rendered on some frame. Blender can suit your needs. You may also keyframe the 3D View drawing of  the [Person] as wire or bounds. The hint of the [Person] may be valuable.


You might even consider changing layer visibility to avoid clutter.
If you have a simple still shot ... you can move objects off the viewable area. This idea is for simple circumstances only.